10,107 research outputs found
The EET Horizontal Tails Investigation and the EET Lateral Controls Investigation
In the energy efficient transport (EET) Horizontal Tails Investigation, aerodynamic data were measured for five different horizontal tails on a full span model with a wide body fuselage. Three of the horizontal tails were low tail configurations and two were T tail configurations. All tails were tested in conjunction with two wings, a current wide body wing and a high aspect ratio supercritical wing. Local downwash angles and dynamic pressures in the vicinity of the tails were measured using a yaw head rake. The results provide a comparison of the aerodynamic characteristics of the two wing configurations at trimmed conditions for Mach numbers between 0.60 and 0.90. In the EET Lateral Controls Investigation, the control effectiveness of a conventional set of lateral controls was measured over a Mach number range from 0.60 to 0.90 on a high aspect ratio supercritical wing semispan model. The conventional controls included a high speed aileron, a low speed aileron, and six spoiler segments. The wing was designed so that the last 25% of the chord is removable to facilitate testing of various control systems. The current status and an indication of the data obtained in these investigations are presented
Two-dimensional cold-air cascade study of a film-cooled turbine stator blade. 1: Experimental results of pressure-surface film cooling tests
The effect of film coolant ejection from the pressure side of a stator blade was determined in a two-dimensional cascade. Stator exit surveys were made for each of six rows of coolant holes. Successive multirow tests were made with two, three, four, five, and six rows of coolant holes open. The results of the multirow tests are compared with the predicted multirow performance obtained by adding the single-row data. Results are presented in terms of stator primary-air efficiency as a function of coolant fraction
Fractionation effects in phase equilibria of polydisperse hard sphere colloids
The equilibrium phase behaviour of hard spheres with size polydispersity is
studied theoretically. We solve numerically the exact phase equilibrium
equations that result from accurate free energy expressions for the fluid and
solid phases, while accounting fully for size fractionation between coexisting
phases. Fluids up to the largest polydispersities that we can study (around
14%) can phase separate by splitting off a solid with a much narrower size
distribution. This shows that experimentally observed terminal polydispersities
above which phase separation no longer occurs must be due to non-equilibrium
effects. We find no evidence of re-entrant melting; instead, sufficiently
compressed solids phase separate into two or more solid phases. Under
appropriate conditions, coexistence of multiple solids with a fluid phase is
also predicted. The solids have smaller polydispersities than the parent phase
as expected, while the reverse is true for the fluid phase, which contains
predominantly smaller particles but also residual amounts of the larger ones.
The properties of the coexisting phases are studied in detail; mean diameter,
polydispersity and volume fraction of the phases all reveal marked
fractionation. We also propose a method for constructing quantities that
optimally distinguish between the coexisting phases, using Principal Component
Analysis in the space of density distributions. We conclude by comparing our
predictions to perturbative theories for near-monodisperse systems and to Monte
Carlo simulations at imposed chemical potential distribution, and find
excellent agreement.Comment: 21 pages, 23 figures, 2 table
Further studies of the coupled chemically reacting boundary layer and charring ablator. Part 1 - Summary Final report
Computer program development for charring ablative materials, chemically reacting laminar boundary layers, and turbulent boundary layer initiatio
Can lay-led walking programmes increase physical activity in middle aged adults? : a randomised controlled trial
Study objective: To compare health walks, a community based lay-led walking scheme versus advice
only on physical activity and cardiovascular health status in middle aged adults.
Design: Randomised controlled trial with one year follow up. Physical activity was measured by questionnaire.
Other measures included attitudes to exercise, body mass index, cholesterol, aerobic capacity,
and blood pressure.
Setting: Primary care and community.
Participants: 260 men and women aged 40–70 years, taking less than 120 minutes of moderate
intensity activity per week.
Main results: Seventy three per cent of people completed the trial. Of these, the proportion increasing
their activity above 120 minutes of moderate intensity activity per week was 22.6% in the advice only
and 35.7% in the health walks group at 12 months (between group difference =13% (95% CI 0.003%
to 25.9%) p=0.05). Intention to treat analysis, using the last known value for missing cases,
demonstrated smaller differences between the groups (between group difference =6% (95% CI -5% to
16.4%)) with the trend in favour of health walks. There were improvements in the total time spent and
number of occasions of moderate intensity activity, and aerobic capacity, but no statistically significant
differences between the groups. Other cardiovascular risk factors remained unchanged.
Conclusions: There were no significant between group differences in self reported physical activity at
12 month follow up when the analysis was by intention to treat. In people who completed the trial,
health walks was more effective than giving advice only in increasing moderate intensity activity above
120 minutes per week
Nonnegative subtheories and quasiprobability representations of qubits
Negativity in a quasiprobability representation is typically interpreted as
an indication of nonclassical behavior. However, this does not preclude states
that are non-negative from exhibiting phenomena typically associated with
quantum mechanics - the single qubit stabilizer states have non-negative Wigner
functions and yet play a fundamental role in many quantum information tasks. We
seek to determine what other sets of quantum states and measurements for a
qubit can be non-negative in a quasiprobability representation, and to identify
nontrivial unitary groups that permute the states in such a set. These sets of
states and measurements are analogous to the single qubit stabilizer states. We
show that no quasiprobability representation of a qubit can be non-negative for
more than four bases and that the non-negative bases in any quasiprobability
representation must satisfy certain symmetry constraints. We provide an
exhaustive list of the sets of single qubit bases that are non-negative in some
quasiprobability representation and are also permuted by a nontrivial unitary
group. This list includes two families of three bases that both include the
single qubit stabilizer states as a special case and a family of four bases
whose symmetry group is the Pauli group. For higher dimensions, we prove that
there can be no more than 2^{d^2} states in non-negative bases of a
d-dimensional Hilbert space in any quasiprobability representation.
Furthermore, these bases must satisfy certain symmetry constraints,
corresponding to requiring the bases to be sufficiently complementary to each
other.Comment: 17 pages, 8 figures, comments very welcome; v2 published version.
Note that the statement and proof of Theorem III.2 in the published version
are incorrect (an erratum has been submitted), and this arXiv version (v2)
presents the corrected theorem and proof. The conclusions of the paper are
unaffected by this correctio
The WAY theorem and the quantum resource theory of asymmetry
The WAY theorem establishes an important constraint that conservation laws
impose on quantum mechanical measurements. We formulate the WAY theorem in the
broader context of resource theories, where one is constrained to a subset of
quantum mechanical operations described by a symmetry group. Establishing
connections with the theory of quantum state discrimination we obtain optimal
unitaries describing the measurement of arbitrary observables, explain how
prior information can permit perfect measurements that circumvent the WAY
constraint, and provide a framework that establishes a natural ordering on
measurement apparatuses through a decomposition into asymmetry and charge
subsystems.Comment: 11 pages, 3 figure
Electrodeposition from supercritical fluids
Recent studies have shown that it is possible to electrodeposit a range of materials, such as Cu, Ag and Ge, from various supercritical fluids, including hydrofluorocarbons and mixtures of CO2 with suitable co-solvents. In this perspective we discuss the relatively new field of electrodeposition from supercritical fluids. The perspective focuses on some of the underlying physical chemistry and covers both practical and scientific aspects of electrodeposition from supercritical fluids. We also discuss possible applications for supercritical fluid electrodeposition and suggest some key developments that are required to take the field to the next stage
ANOPP programmer's reference manual for the executive System
Documentation for the Aircraft Noise Prediction Program as of release level 01/00/00 is presented in a manual designed for programmers having a need for understanding the internal design and logical concepts of the executive system software. Emphasis is placed on providing sufficient information to modify the system for enhancements or error correction. The ANOPP executive system includes software related to operating system interface, executive control, and data base management for the Aircraft Noise Prediction Program. It is written in Fortran IV for use on CDC Cyber series of computers
Particle-particle and quasiparticle random phase approximations: Connections to coupled cluster theory
We establish a formal connection between the particle-particle (pp) random
phase approximation (RPA) and the ladder channel of the coupled cluster doubles
(CCD) equations. The relationship between RPA and CCD is best understood within
a Bogoliubov quasiparticle (qp) RPA formalism. This work is a follow-up to our
previous formal proof on the connection between particle-hole (ph) RPA and
ring-CCD. Whereas RPA is a quasibosonic approximation, CC theory is a correct
bosonization in the sense that the wavefunction and Hilbert space are exactly
fermionic. Coupled cluster theory achieves this goal by interacting the ph
(ring) and pp (ladder) diagrams via a third channel that we here call
"crossed-ring" whose presence allows for full fermionic antisymmetry.
Additionally, coupled cluster incorporates what we call "mosaic" terms which
can be absorbed into defining a new effective one-body Hamiltonian. The
inclusion of these mosaic terms seems to be quite important. The pp-RPA an d
qp-RPA equations are textbook material in nuclear structure physics but are
largely unknown in quantum chemistry, where particle number fluctuations and
Bogoliubov determinants are rarely used. We believe that the ideas and
connections discussed in this paper may help design improved ways of
incorporating RPA correlation into density functionals based on a CC
perspective
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